Plottier Formation
The Plottier Formation is a geologic formation that outcrops in the Argentine Patagonian provinces of Río Negro and Neuquén. It is the younger of two formations belonging to the Río Neuquén Subgroup within the Neuquén Group, with the oldest rocks dating from the late Coniacian and its youngest maybe from the very start of the Santonian. Formerly that subgroup was treated as a formation, and the Plottier Formation was known as the Plottier Member.Sánchez et al. (2006) A section near the Neuquén City airport, north of the town of Plottier, is the type locality of the Plottier FormationFossa Mancini et al. (1938). At its base, this formation grades into the Portezuelo Formation, and it is in turn overlain conformably by the Bajo de la Carpa Formation, a unit of the Río Colorado Subgroup. The Plottier Formation is the smallest formation within the Neuquén Group, with a maximum thickness of only 25 meters. It is differentiated from the underlying Portezuelo Formation primarily by its higher content of argillites (mud deposits) and was deposited under fluvial conditions. In 2006, a detailed lithostratigraphic and paleoecological study of a section of the Plottier Formation was published. This section contained alluvial deposits laid down by what was essentially a low-gradient wandering river throughout the millions of years, but often was of a single-channel type with little meandering.Leanza et al. (2004), Sánchez et al. (2006) Age Era: Mesozoic Period: Late Cretaceous Faunal stage: late Coniacian – ?early Santonian Absolute Age: ~88 to ~86 mya Paleontology Few animal fossils are known from this formation, including: * titanosaurid sauropods (including "Antarctosaurus" giganteus) * a basal coelurosaurian theropod * at least one mammal There are also ichnofossils left on the river's mudflats, as well as fossil freshwater bivalves. See also * List of fossil sites Footnotes References * Chiappe, Luis M. (1993): Enantiornithine (Aves) Tarsometatarsi from the Cretaceous Lecho Formation of Northwestern Argentina. American Museum Novitates 3083: 1-27. with Spanish abstract PDF fulltext * Coria, Rodolfo A.; Currie, Philip J.; Eberth, David & Garrido, Alberto (2002): Bird footprints from the Anacleto Formation (Late Cretaceous), Neuquén, Argentina. Ameghiniana 39(4): 453-463. with Spanish abstract PDF fulltext * Fossa Mancini, E.; Feruglio, E.; Yussen de Campana, J.C. (1938): Una reunión de geólogos de YPF y el problema de la terminología estratigráfica YPF geologists' reunion and the problem of stratigraphy terminology". Boletín de Informaciones Petroleras 15: 1-67. * Leanza, H.A.; Apesteguia, S.; Novas, F.E. & de la Fuente, M.S. (2004): Cretaceous terrestrial beds from the Neuquén Basin (Argentina) and their tetrapod assemblages. Cretaceous Research 25(1): 61-87. (HTML abstract) * Lockley, Martin; Matsukawa, Masaki; Ohira, Hiroto; Li, Jianjun; Wright, Joanna; White, Diane & Chen, Peiji (2006): Bird tracks from Liaoning Province, China: New insights into avian evolution during the Jurassic-Cretaceous transition. Cretaceous Research 27(1): 33-43. (HTML abstract). Erratum: * Salgado, L.; Coria, R.A. & Chiappe, Luis M. (2005): Osteology of the sauropod embryos from the Upper Cretaceous of Patagonia. Acta Palaeontologica Polonica 50(1): 79–92. PDF fulltext * Sánchez, Maria Lidia; Heredia, Susana & Calvo, Jorge O. (2006): Paleoambientes sedimentarios del Cretácico Superior de la Formación Plottier (Grupo Neuquén), Departamento Confluencia, Neuquén paleoenvironments in the Upper Cretaceous Plottier Formation (Neuquen Group), Confluencia, Neuquén. Revista de la Asociación Geológica Argentina 61(1): 3-18. with English abstract PDF fulltext Category:Cretaceous paleontological sites Category:Geology of Argentina